Ingersoll, J. Am. Chem. Soc. (47), 1168-1173 (1925) discusses a method for the resolution of externally compensated acids and bases by which both active forms are obtained completely pure. This method utilizes stereospecific camphorsulfonic acid.
Ingersoll, J. Am. Chem. Soc. (50), 2264-2267 (1928) discusses the resolution of inactive iso-diphenylhydroxy-ethylamine with d and dl-camphor sulfonic acids.